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Gottin Max
02-27-1997, 02:18 AM
Dear All,

I recently( a month ago) wrote the following question:
HI,
I find your name and your e-mail adress on the biomech-i.archives.
I am a french orthopaedic surgeon working on the patellofemoral contact
pressure and their pain. Iwant to measure the forces with a patella
sensors.
Could you tell me if the tekscan sensors are capable of measure
nonperpendiculair forces? and how to get them ?
Your respond is for me very important and I am ready to get these sensors .
By now It is only the choice of the sensors who empeach me to follow up my
Works .
Thaks a lot
My e-mail is : MGottin@sasi.fr




I'd like to thank all those who replied, the information I have recieved
has
been of great use.

Gottin,

I am afraid I am unable to help you. I have not used these sensors.
At the time of my enquiry I was just thinking of feasibility of
pressure measurement on wheelchair seats.

Sorry,

Martin Turner

Dear Gottin,
Our sensors do measure forces on all three axies, Fx, Fy and Fz. I do not
know if they will fit into the space where you would like to use them. I
will have my represenative in France, Mr. Albert Gaudin of Biometrics
France, contact you.
Best regards,
Gary Blanchard

Hello,
F-Scan sensors do NOT measure nonperpendicular or shear forces - in fact
I'm
not sure if there's anything that will currently measure shear forces in
such a small area.
You might do a literature search on Rosenbaum D. He has looked at
pressures
at the subtalar joint and may have useful methods to describe.

The F-Scan address is 451 D Street, Boston MA 02210, phone 1-800-3669.

Good luck!
From: Gottin Max
To: sparto.1
Subject: pressure sensors
Date: Monday, January 20, 1997 7:22PM

Max,

Hello,

Unfortunately, at the time I was doing the search for someone else, and was

not able to follow up on it. So we were not able to purchase the sensors
and I do not know very much about them Sorry that I could not help you.

Pat

From: Gottin Max[SMTP:MGottin@sasi.fr]
Sent: Monday, January 20, 1997 6:30 PM
To: aschmidt@kcc.com
Subject: Tekscan sensors

HI,
I find your name and your e-mail adress on the biomech-i.archives.
I am a french orthopaedic surgeon working on the patellofemoral contact
pressure and their pain. I want to measure the forces with patella
sensors.
Could you tell me if the tekscan sensors are capable of measure
nonperpendiculair forces? and how to get them ?
Your respond is for me very important and I am ready to get these sensors .
By now It is only the choice of the sensors who empeach me to follow up my
Works .
Thanks a lot
My e-mail is : MGottin@sasi.fr

Hello Max,

I worked with Tekscan sensors quite a while and I made the conclusion that
the system provides acceptable pressure data when the sensors are flat and
perpendicular forces are applied to the sensor surface.
As soon as the application induces the sensors to bend and deform you have
an artificial pressure reading caused by bending. This may not be so
dramatic for higher pressure ranges (10 - 100 psi). Since we want to
measure pressures from 0 - 2 psi very accurately the bending causes a too
high variability. I have loked into other pressure systems. If you want I
can give you a contact address in Germany (it is not Emed !)

Tekscan only measures forces perpendicular to its surface !


Regards,

Alex
I'm sorry to say that I don't think the Tekscan sensors are a good choice
to
solve your problems. They are very difficult to calibrate, they're
non-linear, they break easily and are difficult to insert in the knee
joint,
and they can be very expensive to use. However, I have not used the
Tekscan
sensors for over 2 years. It is possible that the company has made
improvements to these sensors that would make them more useful to you. I
did a lot of work to attempt measuring dynamic intra-articular pressures in
the knee joint and found that the Tekscan sensors could not do this
accurately or consistently. However, if you want to contact the Tekscan
company, you can phone them at 1-800-248-3669, or fax them at 617/464-4266.
They are in the Boston area.

There is a workshop on contact mechanics at the Orthopaedic Research
Society
meeting in San Francisco on February 10th, 7:15-8:45 am. If you are able
to
attend this workshop, you will learn about the present state-of-the-art in
contact mechanics. Tom Brown, Gerard Ateshian, Steve Kurtz, and Peter
Walker are doing the workshop. They will review recent experimental and
computational developments for assessing contact stress distributions. You
can learn more about the ORS meeting at the website www.ors.org.


Best of luck with your research.

Jenny

Jennifer L. Pavlovic, Ph.D., P.E.
Research Associate
Spine-Tech, Inc.
Minneapolis, Minnesota

pavl0009@gold.tc.umn.edu

Gottin,

Unfortunately the project I was working on when I enquired about
those pressure sensors did not get very far, so we never bought any
of them.

> I am an orthopaedic surgeon and I am working on the studyof pressure
> on the patella.I was looking for sensors in biomch-I.archives when I
> saw your text. Please, could you tell me if you find the sensors or
> pads containing 2D arrays of sensors? I thank you very much!! Max
>

--------------------------------------------------------------
Martin Turner (TURNER@ODIE.EE.WITS.AC.ZA)
Electrical Engineering Dept, University of the
Witwatersrand, PO Wits, 2050, South Africa.
Tel: +27 11 716-5367; Fax: +27 11 403-1929




Here follows is a summary of the replies I received. At the end of the
document are the references that people supplied/lead me to, for those
interested.